Control architecture and method for two-dimensional optimization of input speed and input power including search windowing

ABSTRACT

A microprocessor driven two dimensional search engine examines transmission operating points within a plurality of search range spaces and assists in determining properties associated with the driveline at various operating points within the space. The size of the space is reduced by rearrangement of data.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/985,227 filed on Nov. 3, 2007, which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure relates generally to control systems forelectro-mechanical transmissions.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known powertrain architectures include torque-generative devices,including internal combustion engines and electric machines, whichtransmit torque through a transmission device to an output member. Oneexemplary powertrain includes a two-mode, compound-split,electromechanical transmission which utilizes an input member forreceiving motive torque from a prime mover power source, preferably aninternal combustion engine, and an output member. The output member canbe operatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Electric machines, operative asmotors or generators, generate a torque input to the transmission,independently of a torque input from the internal combustion engine. Theelectric machines may transform vehicle kinetic energy, transmittedthrough the vehicle driveline, to electrical energy that is storable inan electrical energy storage device. A control system monitors variousinputs from the vehicle and the operator and provides operationalcontrol of the powertrain, including controlling transmission operatingstate and gear shifting, controlling the torque-generative devices, andregulating the electrical power interchange among the electrical energystorage device and the electric machines to manage outputs of thetransmission, including torque and rotational speed.

SUMMARY

A method for decreasing the size of a space from within which atwo-dimensional search engine selects points defined by numerical pairsfor evaluation, the space including at least one two-dimensional firstregion, the first region having minimum and maximum abscissa andordinate values associated with it, includes generating a plurality ofcontour plots, the contour plots having abscissa and ordinate axes, andincluding contours which are representative of a property associatedwith points within the first region bounded by the abscissa and ordinateaxes, selecting a second region from each of the contour plots, thesecond regions each comprising minimum and maximum abscissa values andminimum and maximum ordinate values, providing four tables of data, thedata in each table of the four tables including one of four variablesselected from the group consisting of: the minimum abscissa value, themaximum abscissa value, the minimum ordinate value, and the maximumordinate value, providing a two-dimensional input request, extracting avalue for each of the minimum abscissa value, the maximum abscissavalue, the minimum ordinate value, and the maximum ordinate value fromthe tables, to provide extracted values based upon the input request;,and defining a search space based on the extracted values.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary powertrain, in accordancewith the present disclosure;

FIG. 2 is a schematic diagram of an exemplary architecture for a controlsystem and powertrain, in accordance with the present disclosure;

FIGS. 3-8 are schematic flow diagrams of various aspects of a controlscheme, in accordance with the present disclosure;

FIG. 9 is a schematic power flow diagram, in accordance with the presentdisclosure;

FIG. 10 illustrates one embodiment of a two-dimensional search range orspace, which may be a region definable by coordinate axes withassociated minimum and maximum abscissa and ordinate values, inaccordance with the present disclosure;

FIG. 11 shows a contour plot of energy losses associated with operatingpoints for a transmission as described herein, in accordance with thepresent disclosure; and

FIG. 12 shows one arrangement of data from a plurality of contour plots,in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIG. 1 shows an exemplaryelectromechanical hybrid powertrain. The exemplary electromechanicalhybrid powertrain shown in FIG. 1 comprises a two-mode, compound-split,electromechanical hybrid transmission 10 operatively connected to anengine 14, and first and second electric machines (‘MG-A’) 56 and(‘MG-B’) 72. The engine 14 and first and second electric machines 56 and72 each generate power which can be transmitted to the transmission 10.The power generated by the engine 14 and the first and second electricmachines 56 and 72 and transmitted to the transmission 10 is describedin terms of input torques, referred to herein as T_(I), T_(A), and T_(B)respectively, and speed, referred to herein as N_(I), N_(A), and N_(B),respectively.

In one embodiment, the exemplary engine 14 comprises a multi-cylinderinternal combustion engine which is selectively operative in severalstates to transmit torque to the transmission 10 via an input shaft 12,and can be either a spark-ignition or a compression-ignition engine. Theengine 14 includes a crankshaft (not shown) operatively coupled to theinput shaft 12 of the transmission 10. A rotational speed sensor 11 ispreferably present to monitor rotational speed of the input shaft 12.Power output from the engine 14, comprising rotational speed and outputtorque, can differ from the input speed, N_(I), and the input torque,T_(I), to the transmission 10 due to torque-consuming components beingpresent on or in operative mechanical contact with the input shaft 12between the engine 14 and the transmission 10, e.g., a hydraulic pump(not shown) and/or a torque management device (not shown).

In one embodiment the exemplary transmission 10 comprises threeplanetary-gear sets 24, 26 and 28, and four selectively-engageabletorque-transmitting devices, i.e., clutches C1 70, C2 62, C3 73, and C475. As used herein, clutches refer to any type of friction torquetransfer device including single or compound plate clutches or packs,band clutches, and brakes, for example. A hydraulic control circuit 42,preferably controlled by a transmission control module (hereafter ‘TCM’)17, is operative to control clutch states. In one embodiment, clutchesC2 62 and C4 75 preferably comprise hydraulically-applied rotatingfriction clutches. In one embodiment, clutches C1 70 and C3 73preferably comprise hydraulically-controlled stationary devices that canbe selectively grounded to a transmission case 68. In a preferredembodiment, each of the clutches C1 70, C2 62, C3 73, and C4 75 ispreferably hydraulically applied, selectively receiving pressurizedhydraulic fluid via the hydraulic control circuit 42.

In one embodiment, the first and second electric machines 56 and 72preferably comprise three-phase AC machines, each including a stator(not shown) and a rotor (not shown), and respective resolvers 80 and 82.The motor stator for each machine is grounded to an outer portion of thetransmission case 68, and includes a stator core with electricalwindings extending therefrom. The rotor for the first electric machine56 is supported on a hub plate gear that is operatively attached toshaft 60 via the second planetary gear set 26. The rotor for the secondelectric machine 72 is fixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power, e.g., to vehicle wheels 93, one of which is shownin FIG. 1. The output power is characterized in terms of an outputrotational speed, N_(O) and an output torque, T_(O). A transmissionoutput speed sensor 84 monitors rotational speed and rotationaldirection of the output member 64. Each of the vehicle wheels 93, ispreferably equipped with a sensor 94 adapted to monitor wheel speed, theoutput of which is monitored by a control module of a distributedcontrol module system described with respect to FIG. 2, to determinevehicle speed, and absolute and relative wheel speeds for brakingcontrol, traction control, and vehicle acceleration management.

The input torques from the engine 14 and the first and second electricmachines 56 and 72 (T_(I), T_(A), and T_(B) respectively) are generatedas a result of energy conversion from fuel or electrical potentialstored in an electrical energy storage device (hereafter ‘ESD’) 74. ESD74 is high voltage DC-coupled to the TPIM 19 via DC transfer conductors27. The transfer conductors 27 include a contactor switch 38. When thecontactor switch 38 is closed, under normal operation, electric currentcan flow between the ESD 74 and the TPIM 19. When the contactor switch38 is opened electric current flow between the ESD 74 and the TPIM 19 isinterrupted. The TPIM 19 transmits electrical power to and from thefirst electric machine 56 by transfer conductors 29, and the TPIM 19similarly transmits electrical power to and from the second electricmachine 72 by transfer conductors 31, in response to torque commands forthe first and second electric machines 56 and 72 to achieve the inputtorques T_(A) and T_(B). Electrical current is transmitted to and fromthe ESD 74 in accordance with commands provided to the TPIM which derivefrom such factors as including operator torque requests, currentoperating conditions and states, and such commands determine whether theESD 74 is being charged, discharged or is in stasis at any giveninstant.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive thetorque commands and control inverter states therefrom for providingmotor drive or regeneration functionality to achieve the input torquesT_(A) and T_(B). The power inverters comprise known complementarythree-phase power electronics devices, and each includes a plurality ofinsulated gate bipolar transistors (not shown) for converting DC powerfrom the ESD 74 to AC power for powering respective ones of the firstand second electric machines 56 and 72, by switching at highfrequencies. The insulated gate bipolar transistors form a switch modepower supply configured to receive control commands. There is typicallyone pair of insulated gate bipolar transistors for each phase of each ofthe three-phase electric machines. States of the insulated gate bipolartransistors are controlled to provide motor drive mechanical powergeneration or electric power regeneration functionality. The three-phaseinverters receive or supply DC electric power via DC transfer conductors27 and transform it to or from three-phase AC power, which is conductedto or from the first and second electric machines 56 and 72 foroperation as motors or generators via transfer conductors 29 and 31,depending on commands received which are typically based on factorswhich include current operating state and operator torque demand.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary hybrid powertrain described in FIG. 1. Thedistributed control module system synthesizes pertinent information andinputs, and executes algorithms to control various actuators to achievecontrol objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, and the TPIM 19. A hybrid control module(hereafter ‘HCP’) 5 provides supervisory control and coordination of theECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface(‘UI’) 13 is operatively connected to a plurality of devices throughwhich a vehicle operator may selectively control or direct operation ofthe electro-mechanical hybrid powertrain. The devices present in UI 13typically include an accelerator pedal 113 (‘AP’) from which an operatortorque request is determined, an operator brake pedal 112 (‘BP’), atransmission gear selector 114 (‘PRNDL’), and a vehicle speed cruisecontrol (not shown). The transmission gear selector 114 may have adiscrete number of operator-selectable positions, including therotational direction of the output member 64 to enable one of a forwardand a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality such as antilock braking, traction control, and vehiclestability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the powertrain, serving tocoordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21. Basedupon various input signals from the user interface 13 and thepowertrain, including the ESD 74, the HCP 5 generates various commands,including: the operator torque request (‘T_(O) _(—) _(REQ)’), acommanded output torque (‘T_(CMD)’) to the driveline 90, an engine inputtorque command, clutch torques for the torque-transfer clutches C1 70,C2 62, C3 73, C4 75 of the transmission 10; and the torque commands forthe first and second electric machines 56 and 72, respectively. The TCM17 is operatively connected to the hydraulic control circuit 42 andprovides various functions including monitoring various pressure sensingdevices (not shown) and generating and communicating control signals tovarious solenoids (not shown) thereby controlling pressure switches andcontrol valves contained within the hydraulic control circuit 42.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque command from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input shaft 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters which may include without limitation: a manifoldpressure, engine coolant temperature, throttle position, ambient airtemperature, and ambient pressure. The engine load can be determined,for example, from the manifold pressure, or alternatively, frommonitoring operator input to the accelerator pedal 1 13. The ECM 23generates and communicates command signals to control engine actuators,which may include without limitation actuators such as: fuel injectors,ignition modules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic circuit 42. Inputs from the TCM 17 to the HCP 5 includeestimated clutch torques for each of the clutches, i.e., C1 70, C2 62,C3 73, and C4 75, and rotational output speed, N_(O), of the outputmember 64. Other actuators and sensors may be used to provide additionalinformation from the TCM 17 to the HCP 5 for control purposes. The TCM17 monitors inputs from pressure switches (not shown) and selectivelyactuates pressure control solenoids (not shown) and shift solenoids (notshown) of the hydraulic circuit 42 to selectively actuate the variousclutches C1 70, C2 62, C3 73, and C4 75 to achieve various transmissionoperating range states, as described hereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

Each of the control modules ECM 23, TCM 17, TPIM 19 and BPCM 21 ispreferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and serial peripheral interface buses. The control algorithms areexecuted during preset loop cycles such that each algorithm is executedat least once each loop cycle. Algorithms stored in the non-volatilememory devices are executed by one of the central processing units tomonitor inputs from the sensing devices and execute control anddiagnostic routines to control operation of the actuators, using presetcalibrations. Loop cycles are preferably executed at regular intervals,for example at each 3.125, 6.25, 12.5, 25 and 100 milliseconds duringongoing operation of the powertrain. However, any interval between about2 milliseconds and about 300 milliseconds may be selected.Alternatively, algorithms may be executed in response to the occurrenceof any selected event.

The exemplary powertrain shown in reference to FIG. 1 is capable ofselectively operating in any of several operating range states that canbe described in terms of an engine state comprising one of an engine onstate (‘ON’) and an engine off state (‘OFF’), and a transmission statecomprising a plurality of fixed gears and continuously variableoperating modes, described with reference to Table 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode 1 C1 70 M1_Eng_On ON EVT Mode 1C1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. As anexample, a first continuously variable mode, i.e., EVT Mode 1, or M1, isselected by applying clutch C1 70 only in order to “ground” the outergear member of the third planetary gear set 28. The engine state can beone of ON (‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuouslyvariable mode, i.e., EVT Mode 2, or M2, is selected by applying clutchC2 62 only to connect the shaft 60 to the carrier of the third planetarygear set 28. The engine state can be one of ON (‘M2_Eng_On’) or OFF(‘M2_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O), is achieved. For example, afirst fixed gear operation (‘G1’) is selected by applying clutches C1 70and C4 75. A second fixed gear operation (‘G2’) is selected by applyingclutches C1 70 and C2 62. A third fixed gear operation (‘G3’) isselected by applying clutches C2 62 and C4 75. A fourth fixed gearoperation (‘G4’) is selected by applying clutches C2 62 and C3 73. Thefixed ratio operation of input-to-output speed increases with increasedfixed gear operation due to decreased gear ratios in the planetary gears24, 26, and 28. The rotational speeds of the first and second electricmachines 56 and 72, N_(A) and N_(B) respectively, are dependent oninternal rotation of the mechanism as defined by the clutching and areproportional to the input speed measured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque generative devices comprising the engine 14 and the first andsecond electric machines 56 and 72 to meet the operator torque requestat the output member 64 and transferred to the driveline 90. Based uponinput signals from the user interface 13 and the hybrid powertrainincluding the ESD 74, the HCP 5 determines the operator torque request,a commanded output torque from the transmission 10 to the driveline 90,the input torque from the engine 14, clutch torques for thetorque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission10; and the motor torques for the first and second electric machines 56and 72, respectively, as is described hereinbelow.

Final vehicle acceleration can be affected by other factors including,e.g., road load, road grade, and vehicle mass. The engine state and thetransmission operating range state are determined based upon operatingcharacteristics of the hybrid powertrain. This includes the operatortorque request communicated through the accelerator pedal 113 and brakepedal 112 to the user interface 13 as previously described. Thetransmission operating range state and the engine state may bepredicated on a hybrid powertrain torque demand caused by a command tooperate the first and second electric machines 56 and 72 in anelectrical energy generating mode or in a torque generating mode. Thetransmission operating range state and the engine state can bedetermined by an optimization algorithm or routine which determinesoptimum system efficiency based upon operator demand for power, batterystate of charge, and energy efficiencies of the engine 14 and the firstand second electric machines 56 and 72. The control system managestorque inputs from the engine 14 and the first and second electricmachines 56 and 72 based upon an outcome of the executed optimizationroutine, and system efficiencies are optimized thereby, to manage fueleconomy and battery charging. Furthermore, operation can be determinedbased upon a fault in a component or system. The HCP 5 monitors thetorque-generative devices, and determines the power output from thetransmission 10 at output member 64 that is required to meet theoperator torque request while meeting other powertrain operatingdemands, e.g., charging the ESD 74. As should be apparent from thedescription above, the ESD 74 and the first and second electric machines56 and 72 are electrically-operatively coupled for power flowtherebetween. Furthermore, the engine 14, the first and second electricmachines 56 and 72, and the electromechanical transmission 10 aremechanically-operatively coupled to transfer power therebetween togenerate a power flow to the output member 64.

FIG. 3 shows a control system architecture for controlling and managingsignal flow in a hybrid powertrain system having multiple torquegenerative devices, described hereinbelow with reference to the hybridpowertrain system of FIGS. 1 and 2, and residing in the aforementionedcontrol modules in the form of executable algorithms and calibrations.The control system architecture is applicable to alternative hybridpowertrain systems having multiple torque generative devices, including,e.g., a hybrid powertrain system having an engine and a single electricmachine, a hybrid powertrain system having an engine and multipleelectric machines. Alternatively, the hybrid powertrain system canutilize non-electric torque-generative machines and energy storagesystems, e.g., hydraulic-mechanical hybrid transmissions (not shown).

In operation, the operator inputs to the accelerator pedal 113 and thebrake pedal 112 are monitored to determine the operator torque request.The operator inputs to the accelerator pedal 113 and the brake pedal 112comprise individually determinable operator torque request inputsincluding an immediate accelerator output torque request (‘Output TorqueRequest Accel Immed’), a predicted accelerator output torque request(‘Output Torque Request Accel Prdtd’), an immediate brake output torquerequest (‘Output Torque Request Brake Immed’), a predicted brake outputtorque request (‘Output Torque Request Brake Prdtd’) and an axle torqueresponse type (‘Axle Torque Response Type’). As used herein, the term‘accelerator’ refers to an operator request for forward propulsionpreferably resulting in increasing vehicle speed over the presentvehicle speed, when the operator selected position of the transmissiongear selector 114 commands operation of the vehicle in the forwarddirection. The terms ‘deceleration’ and ‘brake’ refer to an operatorrequest preferably resulting in decreasing vehicle speed from thepresent vehicle speed. The immediate accelerator output torque request,the predicted accelerator output torque request, the immediate brakeoutput torque request, the predicted brake output torque request, andthe axle torque response type are individual inputs to the controlsystem. Additionally, operation of the engine 14 and the transmission 10are monitored to determine the input speed (‘Ni’) and the output speed(‘No’). The immediate accelerator output torque request is determinedbased upon a presently occurring operator input to the accelerator pedal113, and comprises a request to generate an immediate output torque atthe output member 64 preferably to accelerate the vehicle. The predictedaccelerator output torque request is determined based upon the operatorinput to the accelerator pedal 113 and comprises an optimum or preferredoutput torque at the output member 64. The predicted accelerator outputtorque request is preferably equal to the immediate accelerator outputtorque request during normal operating conditions, e.g., when any one ofantilock braking, traction control, or vehicle stability is not beingcommanded. When any one of antilock braking, traction control or vehiclestability is being commanded the predicted accelerator output torquerequest remains the preferred output torque with the immediateaccelerator output torque request being decreased in response to outputtorque commands related to the antilock braking, traction control, orvehicle stability control.

The immediate brake output torque request is determined based upon apresently occurring operator input to the brake pedal 112, and comprisesa request to generate an immediate output torque at the output member 64to effect a reactive torque with the driveline 90 which preferablydecelerates the vehicle. The predicted brake output torque requestcomprises an optimum or preferred brake output torque at the outputmember 64 in response to an operator input to the brake pedal 112subject to a maximum brake output torque generated at the output member64 allowable regardless of the operator input to the brake pedal 112. Inone embodiment the maximum brake output torque generated at the outputmember 64 is limited to −0.2 g. The predicted brake output torquerequest can be phased out to zero when vehicle speed approaches zeroregardless of the operator input to the brake pedal 1 12. When commandedby the operator, there can be operating conditions under which thepredicted brake output torque request is set to zero, e.g., when theoperator setting to the transmission gear selector 114 is set to areverse gear, and when a transfer case (not shown) is set to afour-wheel drive low range.

A strategic control scheme (‘Strategic Control’) 310 determines apreferred input speed (‘Ni_Des’) and a preferred engine state andtransmission operating range state (‘Hybrid Range State Des’) based uponthe output speed and the operator torque request and based upon otheroperating parameters of the hybrid powertrain, including battery powerlimits and response limits of the engine 14, the transmission 10, andthe first and second electric machines 56 and 72. The predictedaccelerator output torque request and the predicted brake output torquerequest are input to the strategic control scheme 31 0. The strategiccontrol scheme 310 is preferably executed by the HCP 5 during each 100ms loop cycle and each 25 ms loop cycle. The desired operating rangestate for the transmission 10 and the desired input speed from theengine 14 to the transmission 10 are inputs to the shift execution andengine start/stop control scheme 320.

The shift execution and engine start/stop control scheme 320 commandschanges in the transmission operation (‘Transmission Commands’)including changing the operating range state based upon the inputs andoperation of the powertrain system. This includes commanding executionof a change in the transmission operating range state if the preferredoperating range state is different from the present operating rangestate by commanding changes in application of one or more of theclutches C1 70, C2 62, C3 73, and C4 75 and other transmission commands.The present operating range state (‘Hybrid Range State Actual’) and aninput speed profile (‘Ni_Prof’) can be determined. The input speedprofile is an estimate of an upcoming input speed and preferablycomprises a scalar parametric value that is a targeted input speed forthe forthcoming loop cycle. The engine operating commands and theoperator torque request are based upon the input speed profile during atransition in the operating range state of the transmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isexecuted during one of the control loop cycles to determine enginecommands (‘Engine Commands’) for operating the engine 14, including apreferred input torque from the engine 14 to the transmission 10 basedupon the output speed, the input speed, and the operator torque requestcomprising the immediate accelerator output torque request, thepredicted accelerator output torque request, the immediate brake outputtorque request, the predicted brake output torque request, the axletorque response type, and the present operating range state for thetransmission. The engine commands also include engine states includingone of an all-cylinder operating state and a cylinder deactivationoperating state wherein a portion of the engine cylinders aredeactivated and unfueled, and engine states including one of a fueledstate and a fuel cutoff state. An engine command comprising thepreferred input torque of the engine 14 and the present input torque(‘Ti’) reacting between the engine 14 and the input member 12 arepreferably determined in the ECM 23. Clutch torques (‘Tcl’) for each ofthe clutches C1 70, C2 62, C3 73, and C4 75, including the presentlyapplied clutches and the non-applied clutches are estimated, preferablyin the TCM 17.

An output and motor torque determination scheme (‘Output and MotorTorque Determination’) 340 is executed to determine the preferred outputtorque from the powertrain (‘To_cmd’). This includes determining motortorque commands (‘T_(A)’, ‘T_(B)’) to transfer a net commanded outputtorque to the output member 64 of the transmission 10 that meets theoperator torque request, by controlling the first and second electricmachines 56 and 72 in this embodiment. The immediate accelerator outputtorque request, the immediate brake output torque request, the presentinput torque from the engine 14 and the estimated applied clutchtorque(s), the present operating range state of the transmission 10, theinput speed, the input speed profile, and the axle torque response typeare inputs. The output and motor torque determination scheme 340executes to determine the motor torque commands during each iteration ofone of the loop cycles. The output and motor torque determination scheme340 includes algorithmic code which is regularly executed during the6.25 ms and 12.5 ms loop cycles to determine the preferred motor torquecommands.

The hybrid powertrain is controlled to transfer the output torque to theoutput member 64 to react with the driveline 90 to generate tractivetorque at wheel(s) 93 to forwardly propel the vehicle in response to theoperator input to the accelerator pedal 113 when the operator selectedposition of the transmission gear selector 114 commands operation of thevehicle in the forward direction. Similarly, the hybrid powertrain iscontrolled to transfer the output torque to the output member 64 toreact with the driveline 90 to generate tractive torque at wheel(s) 93to propel the vehicle in a reverse direction in response to the operatorinput to the accelerator pedal 113 when the operator selected positionof the transmission gear selector 114 commands operation of the vehiclein the reverse direction. Preferably, propelling the vehicle results invehicle acceleration so long as the output torque is sufficient toovercome external loads on the vehicle, e.g., due to road grade,aerodynamic loads, and other loads.

FIG. 4 details signal flow in the strategic optimization control scheme310, which includes a strategic manager 220, an operating range stateanalyzer 260, and a state stabilization and arbitration block 280 todetermine the preferred input speed (‘Ni_Des’) and the preferredtransmission operating range state (‘Hybrid Range State Des’). Thestrategic manager (‘Strategic Manager’) 220 monitors the output speedN_(O), the predicted accelerator output torque request (‘Output TorqueRequest Accel Prdtd’), the predicted brake output torque request(‘Output Torque Request Brake Prdtd’), and available battery powerP_(BAT) _(—) _(MIN) to P_(BAT) _(—) _(MAX). The strategic manager 220determines which of the transmission operating range states areallowable, and determines output torque requests comprising a strategicaccelerator output torque request (‘Output Torque Request AccelStrategic’) and a strategic net output torque request (‘Output TorqueRequest Net Strategic’), all of which are input the operating rangestate analyzer 260 along with system inputs (‘System Inputs’), powercost inputs (‘Power Cost Inputs’), and any associated penalty costs(‘Penalty Costs’) for operating outside of predetermined limits. Theoperating range state analyzer 260 generates a preferred power cost(‘P*cost’) and associated input speed (‘N*i’) for each of the allowableoperating range states based upon the operator torque requests, thesystem inputs, the available battery power and the power cost inputs.The preferred power costs and associated input speeds for the allowableoperating range states are input to the state stabilization andarbitration block 280 which selects the preferred operating range stateand preferred input speed based thereon.

FIG. 5 shows the operating range state analyzer 260 that executessearches in each candidate operating range state comprising theallowable ones of the operating range states, including M1 (262), M2(264), G1 (270), G2 (272), G3 (274), and G4 (276) to determine preferredoperation of the torque actuators, i.e., the engine 14 and the first andsecond electric machines 56 and 72 in this embodiment. The preferredoperation preferably comprises a minimum power cost for operating thehybrid powertrain system and an associated engine input for operating inthe candidate operating range state in response to the operator torquerequest. The associated engine input comprises at least one of apreferred engine input speed (‘Ni*’), a preferred engine input power(‘Pi*’), and a preferred engine input torque (‘Ti*’) that is responsiveto and preferably meets the operator torque request. The operating rangestate analyzer 260 evaluates powertrain operation in M1-Engine Off (264)and M2-Engine Off (266) states to determine a preferred cost (‘P*cost’)for operating the powertrain system responsive to and preferably meetingthe operator torque request when the engine 14 is in the engine-offstate.

FIG. 6 schematically shows signal flow for a 1-dimension search scheme610, executed in each of G1 (270), G2 (272), G3 (274), and G4 (276). Arange of one controllable input, in this embodiment comprising minimumand maximum input torques (‘TiMin/Max’), is input to a 1-D search engine415. The 1-D search engine 415 iteratively generates candidate inputtorques (‘Ti(j)’) which range between the minimum and maximum inputtorques, each which is input to an optimization function (‘OptTo/Ta/Tb’) 440, for n search iterations. Other inputs to theoptimization function 440 include system inputs preferably compriseparametric states for battery power, clutch torques, electric motoroperation, transmission and engine operation, the specific operatingrange state and the operator torque request. The optimization function440 determines transmission operation comprising an output torque, motortorques, and associated battery and electrical powers (‘To(j), Ta(j),Tb(j), Pbat(j), Pa(j), Pb(j)’) associated with the candidate inputtorque based upon the system inputs in response to the operator torquerequest for the candidate operating range state. The output torque,motor torques, and associated battery powers, penalty costs, and powercost inputs are input to a cost function 450, which executes todetermine a power cost (‘Pcost(j)’) for operating the powertrain in thecandidate operating range state at the candidate input torque inresponse to the operator torque request. The 1-D search engine 415iteratively generates candidate input torques over the range of inputtorques. The optimization function 440 determines the transmissionoperation for each candidate input torque. The cost function 450determines the associated power costs. The The 1-D search engine 415identifies a preferred input torque (‘Ti*’) and associated preferredcost (‘P*cost’). The preferred input torque (‘Ti*’) comprises thecandidate input torque within the range of input torques that results ina minimum power cost of the candidate operating range state, i.e., thepreferred cost.

The preferred operation in each of M1 and M2 can be determined byexecuting a 2-dimensional search scheme 620, shown with reference toFIGS. 7 and 8, in conjunction with executing a 1-dimensional searchusing the 1-dimensional search scheme 610 based upon a previouslydetermined input speed which can be arbitrated (‘Input SpeedStabilization and Arbitration’) 615 to determine preferred input speeds(‘N*i’) and associated preferred costs (‘P*cost’) for the operatingrange states.

FIG. 7 shows the preferred operation in each of continuously variablemodes M1 and M2 executed in blocks 262 and 264 of the operating rangestate analyzer 260. This includes executing a 2-dimensional searchscheme 620, shown with reference to FIGS. 6 and 8, in conjunction withexecuting a 1-dimensional search using the 1-dimensional search scheme610 based upon a previously determined input speed which can bearbitrated (‘Input Speed Stabilization and Arbitration’) 615 todetermine preferred costs (‘P*cost’) and associated preferred inputspeeds (‘N*i’) for the operating range states. As described withreference to FIG. 8, the 2-dimensional search scheme 620 determines a afirst preferred cost (‘2D P*cost’) and an associated first preferredinput speed (‘2D N*T’). The first preferred input speed is input to the2-dimensional search scheme 620 and to an adder 612. The adder 612 sumsthe first preferred input speed and a time-rate change in the inputspeed (‘N_(I) _(—) _(DOT)’) multiplied by a predetermined time period(‘dt’). The resultant is input to a switch 605 along with the firstpreferred input speed determined by the 2-dimensional search scheme 620.The switch 605 is controlled to input either the resultant from theadder 612 or the preferred input speed determined by the 2-dimensionalsearch scheme 620 into the 1-dimensional search scheme 610. The switch605 is controlled to input the preferred input speed determined by the2-dimensional search scheme 620 into the 1-dimensional search scheme 610(as shown) when the powertrain system is operating in a regenerativebraking mode, e.g., when the operator torque request includes a requestto generate an immediate output torque at the output member 64 to effecta reactive torque with the driveline 90 which preferably decelerates thevehicle. The switch 605 is controlled to a second position (not shown)to input the resultant from the adder 612 when the operator torquerequest does not include regenerative braking. The 1-dimensional searchscheme 610 is executed to determine a second preferred cost (‘IDP*cost’) using the 1-dimensional search scheme 610, which is input tothe input speed stabilization and arbitration block 615 to select afinal preferred cost and associated preferred input speed.

FIG. 8 schematically shows signal flow for the 2-dimension search scheme620. Ranges of two controllable inputs, in this embodiment comprisingminimum and maximum input speeds (‘Ni Min/Max’) and minimum and maximuminput powers (‘Pi Min/Max’) are input to a 2-D search engine 410. Inanother embodiment, the two controllable inputs can comprise minimum andmaximum input speeds and minimum and maximum input torques. The 2-Dsearch engine 410 iteratively generates candidate input speeds (‘Ni(j)’)and candidate input powers (‘Pi(j)’) which range between the minimum andmaximum input speeds and powers. The candidate input power is preferablyconverted to a candidate input torque (‘Ti(j)’) (412). Each candidateinput speed (‘Ni(j)’) and candidate input torque (‘Ti(j)’) are input tothe optimization function (‘Opt To/Ta/Tb’) 440, for n search iterations.Other inputs to the optimization function 440 include system inputspreferably comprising parametric states for battery power, clutchreactive torques, maximum and minimum torque outputs from the first andsecond electric machines 56 and 72, engine input torque, the specificoperating range state and the operator torque request. The optimizationfunction 440 determines transmission operation comprising an outputtorque, motor torques, and associated battery and electrical powers(‘To(j), Ta(j), Tb(j), Pbat(j), Pa(j), Pb(j)’) associated with thecandidate input power and candidate input speed based upon the systeminputs and the operating torque request for the candidate operatingrange state. The output torque, motor torques, and associated batterypowers, penalty costs and power cost inputs are input to a cost function450, which executes to determine a power cost (‘Pcost(j)’) for operatingthe powertrain at the candidate input power and candidate input speed inresponse to the operator torque request in the candidate operating rangestate. The 2-D search engine 410 iteratively generates the candidateinput speeds and candidate input powers over the range of input speedsand range of input powers. The optimization function 440 determines thetransmission operation for each candidate input speed and candidateinput power. The cost function 450 determines the associated powercosts. The 2-D search engine 410 identifies a preferred input power(‘Pi*’) and preferred input speed (‘Ni*’) and associated preferred cost(‘P*cost’). The preferred input power (‘Pi*’) and preferred input speed(‘Ni*’) comprises the candidate input power and candidate input speedthat result in a minimum power cost for the candidate operating rangestate.

FIG. 9 schematically shows power flow and power losses through hybridpowertrain system, in context of the exemplary powertrain systemdescribed above. There is a first power flow path from a fuel storagesystem 9 which transfers fuel power (‘P_(FUEL)’) to the engine 14 whichtransfers input power (‘P_(I)’) to the transmission 10. The power lossin the first flow path comprises engine power losses (‘P_(LOSS ENG)’).There is a second power flow path which transfers electric power(‘P_(BAT)’) from the ESD 74 to the TPIM 19 which transfers electricpower (‘P_(INV ELEC)’) to the first and second electric machines 56 and72 which transfer motor mechanical power (‘P_(MOTOR MECH)’) to thetransmission 10. The power losses in the second power flow path includebattery power losses (‘P_(LOSS BATT)’) and electric motor power losses(‘P_(LOSS MOTOR)’). The TPIM 19 has an electric power load(‘P_(HV LOAD)’) that services electric loads in the system (‘HV Loads’),which can include a low voltage battery storage system (not shown). Thetransmission 10 has a mechanical inertia power input (‘P_(INERTIA)’) inthe system (‘Inertia Storage’) that preferably include inertias from theengine 14 and the transmission 10. The transmission 10 has mechanicalpower losses (‘P_(LOSS MECH)’) and power output (‘P_(OUT)’). The brakesystem 94 has brake power losses (‘P_(LOSS BRAKE)’) and the remainingpower is transferred to the driveline as axle power (‘P_(AXLE)’).

The power cost inputs to the cost function 450 are determined based uponfactors related to vehicle driveability, fuel economy, emissions, andbattery usage. Power costs are assigned and associated with fuel andelectrical power consumption and are associated with a specificoperating points of the hybrid powertrain. Lower operating costs can beassociated with lower fuel consumption at high conversion efficiencies,lower battery power usage, and lower emissions for each enginespeed/load operating point, and take into account the candidateoperating state of the engine 14. As described hereinabove, the powercosts may include the engine power losses (‘P_(LOSS ENG)’), electricmotor power losses (‘P_(LOSS MOTOR)’), battery power losses(‘P_(LOSS BATT)’), brake power losses (‘P_(LOSS BRAKE)’), and mechanicalpower losses (‘P_(LOSS MECH)’) associated with operating the hybridpowertrain at a specific operating point which includes input speed,motor speeds, input torque, motor torques, a transmission operatingrange state and an engine state.

The mechanical power loss in the transmission 10 includes power lossesdue to rotational spinning, torque transfer, and friction, and operationof parasitic loads, e.g., a hydraulic pump (not shown) for thetransmission 10. The mechanical power loss can be determined for eachoperating range state for the transmission 14 and input speed.Mechanical power loss related to the input speed (‘Ni’) and the outputspeed (‘No’) can be represented by Eq. 1:

P _(MECH LOSS) =a N _(i) +b N _(i) ² +c N _(i) N _(o) +d N _(o) ²   [1]

wherein a, b, c, and d comprise calibrated scalar values determined forthe specific powertrain system and each specific transmission operatingrange state.

Thus, in fixed gear operation, i.e., in one of the fixed gear operatingranges states of G1, G2, G3 and G4 for the embodiment described herein,the power cost input comprising the mechanical power loss to the costfunction 450 can be predetermined outside of the 1-dimension searchscheme 610. In mode operation, i.e., in one of the mode operating rangesstates of M1 and M2 for the embodiment described herein, the power costinput comprising the mechanical power loss to the cost function 450 canbe determined during each iteration of the search scheme 620.

The state stabilization and arbitration block 280 selects a preferredtransmission operating range state (‘Hybrid Range State Des’) whichpreferably is the transmission operating range state associated with theminimum preferred cost for the allowed operating range states outputfrom the operating range state analyzer 260, taking into account factorsrelated to arbitrating effects of changing the operating range state onthe operation of the transmission to effect stable powertrain operation.The preferred input speed (‘Ni_Des’) is the engine input speedassociated with the preferred engine input comprising the preferredengine input speed (‘Ni*’), the preferred engine input power (‘Pi*’),and the preferred engine input torque (‘Ti*’) that is responsive to andpreferably meets the operator torque request for the selected preferredtransmission operating range state. Due to subjective constraintsimposed on a system such as that herein described, the transmissionoperating range state selected may not in all cases be that which istruly optimal from the standpoint of energy usage and power losses.

In one embodiment, such a system may provide a search method fordetermining a desirable input speed for a transmission in a combinationthat comprises at least one torque actuator mechanically coupled to thetransmission, the torque actuator contributing to the input speed ofsaid transmission. One search method includes first selecting apotential operating point for the at least one torque actuator from asearch range, in which the potential operating point has associated withit a transmission input speed value and a transmission input powervalue. For purposes of the disclosure, the term ‘candidate’ can be usedinterchangeably with the term ‘potential’ in describing operating pointsand transmission operating range states. A plurality of power lossesassociated with operation of the combination at the potential operatingpoint is determined, each which is combined to provide a total powerloss for that point. The selection of a potential operating point,determination of power losses and their combination is repeated toprovide a plurality of potential operating points, each of which have atotal power loss associated with them. The potential operating pointsare evaluated for desirability, based on at least one criteria selectedfrom the group consisting of: objective operating criteria andsubjective operating criteria, and one operating point is selected fromthe plurality of potential operating points. Conducting such a searchmethod under the constraint that the output power of said transmissionis kept substantially-constant provides that the contours of the powerlosses (costs) are more prone to be linear when defined in an N_(I),P_(I) plane, thus providing advantageous rapidity for a search enginethat incorporates such methodology to convergence on an operating pointof interest.

A search engine such as 410 can be conceived of as operating on adefined two-dimensional space that contains points corresponding tocandidate N_(I) and P_(I) values for each potential transmissionoperating range state, such as space S as shown in FIG. 10 as the regionon the coordinate axes bounded by P_(I) Min, P_(I) Max, N_(I) Min, andN_(I) Max, wherein P_(I) represents input power to the electromechanicalhybrid transmission and N_(I) is the transmission input speed. The spaceS, which is the search range, is defined using hardware specifications,which typically include electric machine operating speed limits, engineoperating speed limits, transmission output speed, and engine torquelimits. However, in general, the space S is not disposed at a staticlocation on the P_(I), N_(I) coordinate axes, but rather changes itsposition over time in response to operating conditions, which mayinclude changes in operator torque requests and changes in road grade.Changes in the location of the space S on the P_(I), N_(I) coordinateaxes can occur at every iteration of an operational loop in amicroprocessor carrying out the iterations and can occur at intervals asshort as 1 millisecond. Thus, over a few seconds time, the space S mayeffectively sweep out a very large space over potential values withinthe P_(I), N_(I) coordinate axes. In accordance with one embodiment ofthe disclosure, a reduction the effective size of the space S iseffected.

In one embodiment a search engine such as search engine 410 selects,either randomly or according to any desired algorithm, an N_(I) andP_(I) pair present in the space S, and a maximum transmission outputtorque (T_(O) Max) and a minimum transmission output torque (T_(O) Min)associated with the N_(I) and P_(I) pair chosen is calculated based onsystem constraints. Repetition of this method for a large number ofdifferent potential N_(I) and P_(I) pairs provides a plurality ofdifferent T_(O) Min and T_(O) Max values for each potential transmissionoperating range state. The method is repeated for each potentialtransmission operating range state and a plurality of T_(O) Min andT_(O) Max pairs are generated for the space S of and for each potentialtransmission operating range state and N_(I) and P_(I) pairs provided.

From such plurality of different T_(O) Min and T_(O) Max values sogenerated by a search engine for a given potential transmissionoperating range state, the N_(I) and P_(I) pair having the highest T_(O)Max value associated with each potential transmission operating rangestate is generally selected as the preferred N_(I) and P_(I) pair whenan operator torque request is greater than T_(O) Max. In someembodiments for cases in which an operator torque request is less thanT_(O) Min, the potential N_(I) and P_(I) pair associated with the lowestT_(O) Min value is generally selected as the preferred N_(I) and P_(I)for the particular potential transmission operating range state underconsideration. In any event, it is in generally desirable to be able toquickly locate, within a space S for each potential transmissionoperating range state, that N_(I) and P_(I) pair that has the leastpower losses associated with it. The effectiveness of such a task isinhibited by the fact that the location of the space S is movingessentially constantly, which over time makes the effective size of thesearch range of the space S very large.

Towards reduction of the effective size of the space S, pre-calculationsare undertaken in a computer simulation which in one embodiment is notoperatively connected to a drivetrain as described herein. Suchpre-calculations, or off-line simulations, are carried out using valuesfor engine coolant temperature, engine torque curves, battery powerlimits, electric machine speed limits, electric machine torque limits,transmission oil temperature, and battery state-of-charge which arefrequently encountered by a motorized vehicle during its operation, todetermine maximum and minimum values for N_(I) and P_(I) which can beused to define a space S that is smaller in range than the space S thatis encountered during use of a search engine and system useful therewithas herein described. Without use of a method as described herein, thesearch range embraced by the space S was based on N_(I) min and N_(I)max values that were based on speed-based system constraints and P_(I)min and P_(I) max values that were based on T_(I) min and T_(I) maxvalues provided by the ECM 23; however a method as provided hereinnarrows down the search range embraced by the space S, based on off-linesimulation results.

In one embodiment of the disclosure the N_(I), P_(I) plane representingsearch range embraced by the space S is determined by first choosing onepoint in that plane and evaluating it for power losses. Other points arechosen, either arbitrarily or according to any desire algorithm andsimilarly evaluated for power loss if the system were operating at thosepoints. By evaluating, via an off-line computer simulation, a largenumber of points (which may be on the order of 100,000 points), acontour plot such as that shown in FIG. 11 is obtained. The contourlines present in the plot of FIG. 11 represent points having equal powerlosses, or costs associated with operating at those points. The processof generating a plot such as that shown in FIG. 11 is repeated forpoints having different combinations of transmission output speeds andtransmission output torques to provide one such plot as shown in FIG. 11for each N_(O), T_(O) point. By such a method, an off-line “library” ofplots is generated, the number of which plots is determined by thedesires of the programmer, for example, in one embodiment, a librarycontaining about 2500 of such plots is generated.

Thus, according to the foregoing, the search range was determined by anoff-line simulation that evaluates each point in the Ni, Pi plane withinthe “large” search range space S set by system constraints. FIG. 11shows the total power loss (Cost) at an operating point (No, To) in theNi, Pi domain. The steep contour changes represent the violation ofsystem constraints, e.g., To, Ta, Tb, Ti, and P_(Batt). The suggestedsearch range space S excludes operating points that violate systemconstraints and points associated with large costs that are(subjectively) determined as non desirable. For T_(O) points that arebeyond the deliverable T_(O) limits, a torque margin is included in thewindow search determination, so that the window does not shrink to asingle point in the search plane.

From FIG. 11 one can get an idea of locations within the plot where theenergy losses (costs, as expressed in units of power therein) arerelatively small, which is the area labeled B within the highlighted boxin FIG. 11. The space labeled B in FIG. 11 may be determined using analgorithm, one example of which is shown below:

If To > To Max Max − To Margin  Find Ni, Pi Range where (To Max < ToMaxMax −To Margin) &(Ta  penalty Cost < a) &( Tb Penalty Cost < b) &(Tipenalty Cost < c) &  (PBatt Penalty cost ≦d) ElseIf To > To MinMin + ToMargin  Find Ni, Pi Range where (To Min < To MinMin +To Margin) &(Ta penalty Cost < a) &( Tb Penalty Cost < b) &(Ti penalty Cost < c) & (PBatt Penalty cost ≦d) Else  Find Ni, Pi Range where (To Min ≦ To ≦ ToMax) &(Ta penalty Cost  < a) &( Tb Penalty Cost < b) &(Ti penalty Cost <c) &(PBatt  Penalty cost ≦d) &(Objective Power Loss Cost < e) Endin which a, b, c, and d are cost criteria that can reduce the searchrange to exclude operating points that reside outside of the systemconstraints. Setting these values to 0 will exclude all points notwithin the constraints. Setting the values to a small, non-zero positivevalue has the effect of providing a margin around each of the systemconstraints to minimize the effect of simulation errors that couldotherwise erroneously exclude points that are within the constraints.The Ta/Tb/Ti/PBatt penalty costs refer to the costs that are imposed tothe N_(I), P_(I) pair that is associated with Ta, Tb, Ti, PBatt pointsthat are not within their achievable limits. In general, these penaltycosts are provided to increase proportionally with the amount of howmuch each point exceeds each achievable limit. The cost criteria “e” canfurther reduce the search range to exclude points that are within thesystem constraints but have high objective power loss costs subjectivelydetermined as being non-optimal. In the first If step, a ToMax(ToMin) iscalculated for each Ni, Pi point that is evaluated by including theOutput Torque limiting inside the search loop. ToMaxMax (ToMinMin) isthe maximum(minimum) of all ToMax(ToMin), which represents themaximum(minimum) output torque that can be produced within the evaluatedNi, Pi range. In the Else step, the Objective Power Loss cost is the sumof battery power loss, machine power loss, engine power loss, andtransmission power loss.

A process as set forth above with respect to determining the area B onFIG. 11 may be repeated, for each plot that exists in the library thatwas generated during the off-line simulation, to arrive at an area foreach plot that is analogous to area B of FIG. 11. In the hypotheticalcase, such as the one mentioned above in which a library containing 2500of such plots is generated, an area analogous to area B of FIG. 11 isgenerated for each of the 2500 plots. However, the area B of FIG. 11 canbe represented by the four points which define the rectangle of area Btherein, and in a method according to one embodiment of the disclosurein which a library containing 2500 of the aforementioned plots weregenerated, one outcome is a set of four points for each of the 2500plots generated.

An alternate representation of the four points for each of the 2500plots so generated per the foregoing, is to provide four tables of data,each of which four tables of data comprise 2500 entries, and each ofwhich four tables contain values of N_(I) min, N_(I) max, P_(I) min, andP_(I) max, as shown in FIG. 12. Such a table containing N_(I) min valuesis amplified in the bubble of FIG. 12 and is seen to comprise fiftycolumns of N_(O) values and fifty rows of T_(O) values. It is well knownin the art to convert power values to torque values when the rpm isknown. The tables for the N_(I) max, P_(I) min, and P_(I) max aresimilarly structured. Thus, when a vehicle operator makes a powerrequest having N_(O) and T_(O) values associated with it such as isshown at the top of FIG. 12, determination of the N_(I) min valueassociated with such a power request is readily found by reference tothe N_(I) min table. For example, if the operator power requestcomprises an N_(O) value of 1000 rpm and a T_(O) value of 1500Newton*Meters, a microprocessor refers to the table for the N_(I) minvalues and simply finds the box having the location 1000, 1500 andextracts the value for N_(I) min(a). In like fashion, values for N_(I)max, P_(I) min, and P_(I) max for the operator torque request having anN_(O) value of 1000 rpm and a T_(O) value of 1500 Newton*Meters arereadily extracted from the other three tables. As one of ordinary skillin the art readily recognizes, the number of plots generated being 2500in this one example was chosen for illustrative purposes, and anydesired number of plots may be generated. The values of the parametersN_(O) and T_(O) in the example of FIG. 12 are discrete numbers, and fordetermining numerical values of N_(O) and T_(O) which reside between thevalues of the rows and columns, simple mathematical interpolation isemployed.

Thus, a method for determining a set of values for N_(I) min, N_(I) max,P_(I) min, and P_(I) max for input to a 2-D search engine such as 410has been provided, and these values of N_(I) min, N_(I) max, P_(I) min,and P_(I) max are sufficient to define search range space S having asubstantially smaller size than what is otherwise provided by a systemas described herein. This decreased size of the space S provided by amethod according to this disclosure translates to decreased demand oncomputer resources and accordingly results in more efficient searchingand faster pinpointing of exact operating points for potentialtransmission operating modes.

It is understood that modifications are allowable within the scope ofthe disclosure. The disclosure has been described with specificreference to the preferred embodiments and modifications thereto.Further modifications and alterations may occur to others upon readingand understanding the specification. It is intended to include all suchmodifications and alterations insofar as they come within the scope ofthe disclosure.

1. Method for decreasing the size of a space from within which atwo-dimensional search engine selects points defined by numerical pairsfor evaluation, said space comprising at least one two-dimensional firstregion, said first region having minimum and maximum abscissa andordinate values associated with it, said method comprising: generating aplurality of contour plots, said contour plots having abscissa andordinate axes, and comprising contours which are representative of aproperty associated with points within the first region bounded by saidabscissa and ordinate axes; selecting a second region from each of saidcontour plots, said second regions each comprising minimum and maximumabscissa values and minimum and maximum ordinate values; providing fourtables of data, the data in each table of said four tables comprisingone of four variables selected from the group consisting of: saidminimum abscissa value, said maximum abscissa value, said minimumordinate value, and said maximum ordinate value; providing atwo-dimensional input request; extracting a value for each of saidminimum abscissa value, said maximum abscissa value, said minimumordinate value, and said maximum ordinate value from said tables, toprovide extracted values based upon said input request; and defining asearch space based on said extracted values.
 2. A method as in claim 1further comprising: searching said search space to determine a desirablepoint, based on any pre-selected criteria.
 3. A method as in claim 2wherein said searching is conducted using an algorithm.
 4. A method asin claim 1 wherein said property is power loss associated with adrivetrain for points located within said first region, said firstregion having coordinates of transmission input speed and transmissioninput power.
 5. A method as in claim 1 wherein said numerical pairs eachcomprise a transmission input speed value and a transmission input powervalue.
 6. A method as in claim 1 wherein said numerical pairs selectedfor evaluation are each associated with a value obtained by summing atleast two power losses associated with a driveline of a motorizedvehicle when operating in a continuously-variable mode at pointsrepresented by said numerical pairs within said space.
 7. A method as inclaim 1 wherein said input request comprises two coordinates, said twocoordinates comprising at least one of the same coordinates used as adefining variable in each table of said four tables.
 8. A method as inclaim 1 wherein said second region comprises less area on atwo-dimensional plane than said first region.
 9. A method as in claim 1wherein said first region undergoes a change of position within saidtwo-dimensional plane as a function of time.
 10. Method for controllinga powertrain system which includes an engine, and a transmission, thetransmission operative in one of a plurality of operating modes totransfer power between the engine and an output member, the methodcomprising: defining a two-dimensional space within which space residescandidate operating points for said transmission, the candidateoperating points each comprising a transmission input speed and atransmission input power value; searching said two-dimensional space todetermine an operating point to be chosen based on pre-selectedcriteria; and selectively commanding said powertrain system to operateusing a transmission input speed and a transmission input power valueassociated with a chosen point from within said two-dimensional space.11. A method according to claim 10 wherein said pre-selected criteriaincludes a summation of at least two power losses associated with saidpowertrain system.
 12. A method according to claim 10 furthercomprising: defining a smaller two-dimensional space within saidtwo-dimensional space within which said searching is to be carried out.13. A method according to claim 12 further comprising: searching saidsmaller two-dimensional space to determine an operating point to bechosen based on pre-selected criteria.
 14. A method according to claim13 further comprising subsequently selectively commanding saidpowertrain system to operate using a transmission input speed and atransmission input power value associated with a chosen point fromwithin said smaller two-dimensional space.
 15. A method according toclaim 12 wherein said smaller two-dimensional space is determined byoff-line simulations of operating parameters which are provided inreference to said powertrain system.
 16. A method according to claim 15wherein at least one of said operating parameters is subjective.
 17. Asearch method for determining a desirable input speed for a transmissionin a combination that comprises at least one torque actuatormechanically coupled to said transmission, said torque actuatorcontributing to the input speed of said transmission, comprising:selecting a potential operating point for said at least one torqueactuator from a search range, said potential operating point havingassociated with it a transmission input speed value and a transmissioninput power value; determining a plurality of power losses associatedwith operation of said combination at said potential operating point;combining said power losses of said plurality, to provide a total powerloss; repeating said selecting, said determining, and said combining, toprovide a plurality of potential operating points, each of which have arespective total power loss associated therewith; evaluating saidplurality of potential operating points for desirability, based on atleast one criteria selected from the group consisting of: objectiveoperating criteria and subjective operating criteria; and selecting oneoperating point from said plurality of potential operating points; saidsearch method being conducted under the constraint of maintaining theoutput power of said transmission at least substantially-constant, andoptionally, constant.
 18. A method according to claim 17, furthercomprising: selectively commanding a change in the transmissionoperating range state based on said one operating point selected.